Means to inhibit overglaze damage by automatic dishwashing detergents

ABSTRACT

A CLEANING COMPOSITION PARTICULARLY ADAPTED FOR WASHING DISHES, GLASSES AND SILVERWARE IN MECHANICAL DEVICES SUCH AS AUTOMATIC DISHWASHERS AND CAPABLE OF INHIBITING OVER-GLAZE ATTACK CONTAINING AS AN ESSENTIAL INGREDIENT METALLIC ALUMINUM OR ALUMINIUM ALLOY.

lO-3l-7Z AU 165 EX 3,701,736 MEANS T INHIBIT OVERGLAZE DAMAGE BY AUTOMATIC DISHWASHING DETERGENTS Amory Earl Austin, Colonia, and Charles L. Bechtold, Edison, N.J., assignors to Colgate-Palmolive Company, New York, N.Y. No Drawing. Filed Apr. 12, 1971, Ser. No. 133,340 Int. Cl. Clld 7/18, 7/56 US. Cl. 252-99 9 Claims ABSTRACT OF THE DISCLOSURE A cleaning composition particularly adapted for washing dishes, glasses and silverware in mechanical devices such as automatic dishwashers and capable of inhibiting over-glaze attack containing as an essential ingredient metallic aluminum or aluminium alloy.

The present invention relates in general to cleaning compositions and in particular to the provision of cleaning compositions beneficially adapted for use in connection with the cleaning of substrates such as dishware and the like having a glazed surface.

Many of the cleaning compositions heretofore recommended for use in connection with the cleaning of substrates having a glazed surface have been subject to one or more significant disadvantages. Perhaps the paramount difficulty involved relates to the pronounced tendency of such compositions to attack or otherwise deleteriously affect substrates such as typified by glass, porcelain, aluminumware and the like, thereby leading to impairment of such articles. As will be recognized, aesthetic considerations rather than purely functional criteria are often of overriding importance as regards to suitability of a given cleaning composition and especially when contemplated for use in connection with the cleaning of fine china and the like having an ornamental or decorative surface. The magnitude of the problems encountered can be readily appreciated in view of the significant risk of economic loss entailed. Without intending to be bound by any theory, it has nevertheless been hypothesized in explanation of the overglaze attack phenomenon that one or more of the ingredients present in the cleaning com position exhibit a pronounced if not intolerable tendency to attack the flux constitutents present in the bonding material utilized in securing the decorative or ornamental pattern to the substrate and especially under the relatively severe alkaline conditions necessarily extant in the cleaning solution during actual use.

In an effort to overcome or otherwise ameliorate the foregoing and related dilficulties, considerable research activity has been necessary in the development of cleaning compositions specifically and advantageously adapted to minimize the over-glaze attack problem and yet capable of providing the requisite measure of cleaning activity. Thus, much of the methodology heretofore promulgated involves as an essential expedient the use of one or more additives which purportedly function as inhibitors under the conditions normally encountered in cleaning. 'In this regard, a variety of such inhibitor additives, has been recommended by the prior art such as aluminum formate, aluminum acetate, alkali metal aluminum orthophosphates, and alkali aluminate, zincate or berylliate. Although providing relatively efiective means whereby to enable substantial alleviation of the overglaze attack problem, the overall advantage realized is often marginal in view of concomitant problems having as their genesis the objectionable tendency of the cleaning composition and more particularly, the inhibitor compound, to yield unsightly deposits or precipitates on the surface of the substrate treated, not to mention the contacting surfaces of the washing receptable. As will be recognized, the fugitive behavior of the inhibitor material may be such as to substantially vitiate any advantage which might otherwise accrue from its use thereby detracting from commercial feasibility.

The insurmountable nature of the foregoing problem is made manifestly clear by reference to the fact that the residue problem is seemingly exacerbated as the relative concentration of the inhibitor in the cleaning composition is increased and particularly when increased to values acknowledged as being mandatory for purposes of achieving truly optimum effects. Thus, it has been ascertained that those quantities of inhibitor invariably found to be necessary for effective negotiation of the overglaze attack problem correspond to those quantities found to be particularly offensive as regards precipitate formation.

Accordingly, it has now been discovered that the inclusion of a quantity of metallic aluminum (including aluminum alloy) in the detergent formulation or as metal strips in the dishwasher surprisingly inhibits attack on Another object of the present invention resides in the.

provision of cleaning compositions capable of providing superior cleaning activity, eg bleaching, washing, etc.

Other objects and advantages of the present invention will become more apparent hereinafter as the description proceeds.

In accordance with the present invention a watersoluble alkaline detergent composition for automatic dishwashing comprises a major amount of water soluble organic and/or inorganic builder salts; and metallic aluminum as a protector against overglaze attack.

The metallic aluminum contemplated for use in the practice of the present invention and capable of inhibiting both overglaze attack and attack on aluminumware may be in the form of metal strips hung in the dishwasher during the washing cycles or in comminuted form as a direct additive to the detergent formulation. The metallic aluminum may be sacrificial aluminum, aluminum alloys, or pure aluminum. The preferred form of aluminum is in the form of a powder because of the ease with which it can be formulated into a dishwasher detergent, although any finely divided aluminum may be utilized herein. The use of metallic aluminum in lieu of aluminum compounds, heretofore utilized in dishwashing formulations, eliminates stability and solubility problems associated with said aluminum compounds under actual use conditions which may result in undesirable residues found in the cup receptacles and/or on the glassware and dishware. The metallic aluminum additive, which is readily soluble in acids or alkalis, permits greater freedom in the formulation of dishwasher cleaning products, capable of protecting the overglaze pattern on fine china and the aluminumware from attack by the alkaline washing solution, without adversely affecting the cleaning efiicacy of the detergent. The superior protection afforded by metallic aluminum is illustrated by the following test, wherein a 4" x 1" x 3& strip of utensil grade aluminum was immersed in 3,000 mi. of 0.15% concentration detergent soluiton for two hours at 211 F. The metal strip lost 0.0650 gram of aluminum, establishing that 0.000022 g./bl. of aluminum metal (or 1.5% aluminum metal in the detergent formula) significantly inhibited damage to the overglaze pattern. It has been found that an amount as low as 0.25% of metallic aluminum in the product is effective in inhibiting overglaze attack. .A desirable criterion appears to be the presence of a minimum of 20 micrograms of metallic aluminum per ml. of aqueous washing solution.

The water soluble builder salts utilized in the instant detergent composition comprises one or more inorganic and/or organic basic and neutral water soluble salts. The builder salts are employed in amounts ranging up to about 95%, i.e. 40-95% by weight with a range of from about 60% to about 90% by weight of the composition being preferred. Suitable inorganic builders include without necessary limitation, trisodium phosphate, tetrasodium pyrophosphate, sodium acid pyrophosphate, sodium tripolyphosphate hexahydrate, sodium monobasic phosphate, sodium dibasic phosphate, sodium hexameta phosphate, sodium silicates, SiO /Na O of 1/1 to 3.2/1, e.g. (sodium metasilicate), sodium carbonate, sodium sulfate, borax, etc. Other alkali metal salts such as potassium and lithium; ammonium and substituted ammonium salt such as methylammonium, diethanolammonium and triethanolammonium; and amine salts such as mono-, diand trietthanolamine, methylamine, octylamino, diethylenetn'amine, triethylenetetramine and ethylenediamine are efiicacious. Suitable organic builders include salts of organic acids and, in particular, the water soluble salts of aminopolycarboxylic acids and hydroxycarboxylic acids. The acid portion of the salt can be derived from acids such as nitrilodiacetic; N-(2-hydroxyethyl) nitrilodiacetic acid, nitrilotriacetic acid (NTA), ethylenediamine tetracetic acid (EDTA); N-(2- hydroxyethyl) ethylenediamine triacetic acid; 2-hydroxyethyl iminodiacetic acid; 1,2-diaminocyclohexanediacetic acid; diethylenetriamine penta-acetic acid, citric acid and the like. The builder salt is preferably employed in amounts sutficient to yield a pH in water of from 9.5 to 12 preferably from 10 to 11 in order to obtain optimum detergency performance.

The cleaning compositions described herein may further be provided with one or more bleaching agents which may in general be defined as encompassing compounds capable of liberating a hypohalite such as hypochlorite chlorine and/or hypobromite bromine on contact with aqueous media. Particular examples of bleaching agents include the dry, particulate heterocyclic N-bromo and N-chloro imides such as trichloro-cyanuric, tribromocyanuric acid, dibromoand dichlorocy-anuric acid, the salts thereof with water-solubilizing cations such as potassium and sodium and mixtures thereof. Particular compounds found useful are potassium dichloroisocyanurate and trichloroisocyanuric acids.

Other N-bromo and N-chloro imides may also be used, such as N-brominated and N-chlorinated succinimide, malonimide phthalimide and naphthalimide. Other compounds include the hydantoins, such as 1,3-dibromo and 1,3-dich1oro 5,5-dimethylhydantoin; N-monochloro-5,5- dimethylhydantoin, methylene bis(N-bromo-5,5-dimethylhydantoin); 1,3-dibromo and 1,3-dichloro -isobutylhydantoin; 1,3-bromo and 1,3-dichloro, S-methyl-S-n-amylhydantoin, and the like. Other useful hypohalite-liberating agents comprise tribromomelamine and trichloromelamine. Dry, particulate, water soluble anhydrous inorganic salts are likewise suitable for use such as lithium hypochlorite and hypobromite. The hypohalite-liberating agent may, if desired, be provided in the form of a stable, solid complex or hydrate, such as sodium p-toluene-su lfo-bromamine-trihydrate, sodium benzene sulfo-chloramine-dihydrate, calcium hypobromine tetrahydrate, calcium hypochlorite tetrahydrate etc. Brominated and chlorinated trisodium phosphate formed by the reaction of the corresponding sodium hypohalite solution with trisodium phosphate (and water as necessary) likewise comprise efiicacious materials. The present invention contemplates as an additional embodiment the use of bleaching agents capable of liberating hypochlorite as Well as hypobromite such as, for example, the N-brominated, N'- chlorinated heterocyclic imides, as for example the N- bromo, N'-chlorocyanuric acids and salts thereof, e.g., N-monobromo-N, N-dichloro-cyanuric acid, N monobromo-N-monochlorocyanuric acid, sodium-N-monobromo-N monochlorocyanurate, potassium-N-monobromo- N-monochlorocyanuate; and the N-brominated, N-chlorinated hydantoins, e.g., N-bromo-N-chloro-5,5-dimethylhydantoin and N-bromo-N-chloro-S-ethyl-S-methyl hydantoin.

The hypohalite-liberating compound is employed in an amount of from 0.5 to 5% by weight of the composition, and preferably in an amount of from about 0.5 to 3% by weight thereof. In any event, the hypohalide material should preferably be employed in amounts sufficient to yield from about 0.53% available chlorine, bromine etc. in order to assure optimum results.

In general, efiicacious cleaning compositions may be formulated in accordance with the present invention by the use of metallic aluminum in amounts of about 0.06 to 3% by weight of total composition and up to about i.e. from 40% to 95% by weight of at least one compound selected from the group of water-soluble organic detergent, water soluble inorganic or organic neutral or alkaline builder salt, bleaching agent capable of liberating hypohalite on contact with aqueous media and caustic alkali. The bleaching agent is essential to the implementation of those embodiments of the present invention directed to industrial bottle cleaning compositions.

Water soluble organic detergents, i.e. surface active components may be employed, such materials being well known in the prior art, the term detergent comprehending species of the anionic, cationic, amphoteric and zwitterionic types. In formulating an automatic dishwasher product, it is preferred to utilize alow foaming detergent such as the non-ionics.

Nonionic surface active agents include those surface active or detergent compounds which contain an organic hydrophobic group and a hydrophilic group which is a reaction product of a solubilizing group such as carboxylate, hydroxyl, amido or amino with ethylene oxide or with the polyhydration product thereof, polyethylene glycol.

As examples of nonionic surface active agents which may be used there may be noted the condensation prodnets of alkyl phenols with ethylene oxide, e.g., the reaction product of isooctyl phenol with about 6 to 30 ethylene oxide units; condensation products of alkyl thiophenols with 10 to 15 ethylene oxide units; condensation products of higher fatty alcohols of monoethers of hexahydric alcohols and inner ethers thereof such as sorbitan monolaurate, sorbital mono-oleate and mannitan monopalrnitate, and the condensation products of polypropylene glycol with ethylene oxide.

Further suitable detergents are polyoxyalkene esters of organic acids, such as the higher fatty acids, rosin acids, tall oil, or acids from the oxidation of petroleum, and the like. The polyglycol esters will usually contain from about 8 to about 30 moles of ethylene oxide or its equivalent and about 8 to 22 carbon atoms in the acyl group. Suitable products are refined tall oil condensed with 16 or 20 ethylene oxide groups, or similar polyglycol esters of lauric, stearic, oleic and like acids.

Additional suitable non-ionic detergents are the polyalkylene oxide condensates with higher fatty acid amides, such as the higher fatty acid primary amides and higher fatty acid monoand di-ethanol amides. Suitable agents are coconut fatty acid amide condensed with about 10 to 30 moles of ethylene oxide. The fatty acyl group will similarly have about 8 to 22 carbon atoms, and usually about 10 to 18 carbon atoms in each product. The corresponding sulphonamides may also be used if desired.

Otherf suitable polyether non-ionic detergents are the polyalkylene oxide ethers of higher aliphatic alcohols. Suitable alcohols are those having a hydrophobic character, and preferably 8 to 22 carbon atoms. Examples thereof are iso-octyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl and oleyl alcohols which may be condensed with an appropriate amount of ethylene oxide, such as at least about 6, and preferably about 10-30 moles. A typical product is tridecyl alcohol, produced by the Oxo process, condensed with about l2, 15 or 20 moles of ethylene oxide. The corresponding higher alkyl mercaptan or thioalcohols condensed with ethylene oxide are also suitable for use in compositions of the present invention.

Examples of other suitable wetting agents include low foaming anionic materials usch as dodecyl hydrogen phosphate, methyl naphthalene sulfonate, sodium 2-acetamidohexadecane-l-sulfonae, and mixtures thereof. Mixtures of the foregoing wetting agents may also be employed, and, if desired, foam-reducing additive may be added as appropriate to minimize undesirable foaming tendencies of these wetting agents under conditions of use.

The detergent material is employed in concentrations ranging from about 0.5% to about by weight of total composition with a range of 1% to 3% being particularly preferred.

Thus, a relatively minor amount of nonionic type detergent, that is, about 2-4% is especially beneficial inasmuch as it acts as a foam depressant as well as detersive agent in an automatic dishwashing solution.

Minor amounts of other additives which do not interfere with the cleaning, anticorrosive, and overglaze protection properties of instant composition may be added such as pigments, dyes, perfume, fillers, extenders, suds builders, suds depressors, anti-redeposition agents, etc. In some instances it may be commercially feasible to add said ingredients to render them more attractive to the consumer.

The following examples are given for purposes of illustration only and are not to be considered as necessarily constituting a limitation on the present invention. All parts and percentages given are by weight unless otherwise indicated. For purposes of ascertaining the capacity of the various compositions exemplified to ameliorate overglaze attack on fine china samples, the method of the Chemical Specialties Manufacturers Association (CSMA) is employed, such method being described in detail in Soap and Chemical Specialities," 33 (9), 60, 1957. Such test is designed as an accelerated dishwasher exposure method; thus, the comparative removal of overglaze decoration provides direct means for aflording an evaluation of the corrosiveness of dishwashing detergent solutions. According to such method, samples of standard plates (Greenwood pattern) Onondaga Pottery Co., Syracuse, N.Y. are immersed in deionized or distilled water maintained at a temperature of 211 F. and containing the indicated percent concentration of detergent for periods of 2, 4 and 6 hours. The test samples are thereafter removed, hand-rubbed with cloth and compared with untreated samples of the same standard plate. The treated samples are visually scrutinized to determine the extent of overglaze damage with numerical indicia being assigned to indicate the extent of overglaze damage involved. Thus, the scale of 0, 1, 2, 3 and 4 correspond, in terms of damage, to none, slight, moderate, considerable and complete respectively.

EXAMPLE 1 This example illustrates the applicability of the present invention to the preparation and use of cleaning compositions specifically adapted for use in connection with dishwashing operations. The following composition is prepared by dry-blending the specified ingredients to form a dry particulate composition.

Ingredients: Percent Sodium tripolyphosphate hexahydrate 66.48 Sodium metasilicate, anhydrous 20.0

Sodium sulfate, anhydrous 4.0-

5 Non-ionic detergent 1 1.5 Color solution 0.40 Perfume 0.02 Potassium dichloroisocyanurate' 1.60

10 Boric oxide 6.0

The non-ionic detergent is the product obtained by the condensation of about three mols of propylene oxide with the condensation product of one mole of a. mixture of essentially straight chain, primary. fatty alcohols in the Cio-Cm range with about six mols of ethylene oxide.

An aluminum metal strip 4" x 1" x $5 was immersed in a 0.15% aqueous solution of the above ingredients having a pM of about 10.3 containing samples of Greenwood china for 2 hours, 4 hours and 6 hours.

The following results are obtained:

Al strip weight Weight grams diflerpH Time, ence, CSMA, hours Before After grams Before After rating 2 B 87895 8.81395 -o. 06500 10.3 10.9 +0 -0.3939o 10.2 9.5 0 6 0.40620 10.4 9.9 0

As the above data makes manifestly clear, no perceptible overglaze damage is detected even after 6 hours immersion. Equally important is the fact that these samples are substantially devoid of aluminum precipitate, thereby yielding an aesthetically pleasing surface. This same composition without the aluminum strip exhibited CSMA ratings of 1, 2, and 3 after 2, 4 and 6 hours immersion, respectively, which is indicative of slight to moderate damage to the overglaze on fine china. Considering that each washing period is approximately /2 hour, overglaze damage is evident after four washings.

Overglaze damage evaluated according to the CSMA method utilizing a 0.15% aqueous solution of the above granular composition having an initial pH of about 10.7 and after 6 hours immersion a pH of about 10.4 is 0.

EXAMPLE 3 Example 2 is repeated except that the concentration of the aluminum powder is reduced to 1.0% and the sodium sulfate is increased to 8.63%. The results obtained are a CSMA rating of 0, a pH of about 10.4 before and a pH of about 10.2 after 6 hours immersion.

EXAMPLE 4 Example 2 is repeated except that the concentration of the aluminum powder is reduced to 0.5% and the sodium sulfate is increased to 9.13%. The results obtained is a CSMA rating of 0+ and an initial and final pH of about 10.4.

A 0.5% aqueous concentration of the above ingredients also exhibited a CSMA rating of 0 after 6 hours immersion. Thus, it is apparent that amounts as low as 0.5 metallic aluminum is sufiicient to effectively protect overglaze patterns at normal use concentrations.

EXAMPLES 5 AND 6 Example Ingredients 5 6 Sodium trlpolyphosphate hexaliydrate Sodium trlpolyphosphate, anhydrous Sodium metasilicate, anhydrous...-

Sodium sulfate, anhydrous 4 Sodium chloride, anhydrous 20. 446

N on-ionlc detergent, Example 1...- 1. 2. 752

c or 0.145 0.145

Propylene glycol 0. 034 0. 034

Magnesium silicate 2.00 2.00

Aluminum powder 0. 256 0. 256

EXAMPLE 7 Ingredients: Percent Sodium citrate .2H O 45.0

Non-ionic detergent, Ex. 1 2.0

Potassium dichloroisocyanurate 2.0

Sucrose 6.0

Sodium metasilicate 10.0

Sodium carbonate 20.0

Sodium sulfate 8.744

I Boric acid 3.0

Boric oxide 3.0

Aluminum dust 0.256

The pH of a 1% solution of the above ingredients is about 10.4. Overglaze tests at 0.15% concentration gave a CSMA rating of 0+ after 6 hours immersion.

EXAMPLE 8 Example 7 is repeated but the boric acid and the boric oxide are omitted with an increase of the sodium sulfate content to 14.744%. The pH of a 1% solution of these ingredients is about 11.4. The CSMA rating of a 0.15 solution hereof is 0+.

The above results are indicative of the complete protection against overglaze attack for long immersion periods afforded by the presence of even very small amounts of metallic aluminum, on the order of about 0.25% by weight of the total composition.

When the foregoing procedure is repeated but the metallic aluminum omitted, slight incipient overglaze attack is detected for immersion periods of 2 hours, moderate attack after 4 hours immersion and considerable attack after 6 hours immersion.

In addition, the exemplified procedure makes unavoidably clear that the compositions provided in accordance with the present invention are capable of superior cleaning activity i.e., displaying an outstanding capacity to readily remove stain deposits from a wide variety of glazed dishware.

Effective industrial bottle cleaning compositions may be provided in accordance with the present invention by merely admixing with caustic alkali whereby to provide a highly alkaline composition preferably having a pH of about 12. Such compositions may be readily formulated in accordance with the parameters hereinbefore described.

Results similar to those described in the foregoing examples are obtained when the procedures delineated therein are repeated but employing in lieu of the specific non-ionic detergent identified a variety of material selected from nonionic, anionic, cationic, amphoteric and zwitterionic types. Moreover, various bleaching agents hereinbefore recommended for such purposes may be readily employed to advantage.

While the detergent composition of the present invention finds most efficacious utilization in connection with the washing of the dishes and the like in automatic dishwashers, naturally, the detergent may be utilized in other fashions as desired. Usually, however, the best mode of 8 use will be in connection with automatic dishwashers which have the ability of dispensing the detergent of the present invention in one or more separate wash cycles. Accordingly, the detergent compositions of the present invention is added to the two receptacles, if such are present, in an automatic dishwasher. When the dishwasher is set into operation, after the dishes have been suitably positioned therein, the automatic devices of the dishwasher permit the addition of sufficient water to produce a concentration of the detergent composition of approximately 0.15 to 0.5% by weight. The operation of the dishwasher results in treating, that is, washing of the dishes with the aqueous solution of the detergent composition. Usually, the sequence of operation in utilizing an automatic dishwasher results in one or more rinsing steps following the one or more washing cycles. In utilizing the detergent composition of the present invention it will be noted that even after use in considerable number of washings there will be little or no attack on the overglaze on china or little or no attack on aluminum- Ware as a result of the use of the detergent composition.

Similarly any dishwasher detergent may be utilized in accordance with this invention by including within the confines of the dishwasher strips of aluminum or aluminum alloy which will supply metallic aluminum ions to said wash solution during operation.

It will be apparent that many changes and modifications of the several features described herein may be made without departing from the spirit and scope of the invention. It is therefore apparent that the foregoing description is by way of illustration of the invention rather than limitation of the invention.

What is claimed is:

1. A water-soluble alkaline detergent composition capable of inhibiting overglaze attack and providing an alkaline pH in water consisting essentially of about 40-95% by weight of at least one water-soluble organic and/or inorganic alkaline or neutral builder salt, and at least 3.25% by weight of metallic aluminum.

2. A composition in accordance with claim 1, which also includes about 0.5% by weight of a bleaching agent capable of liberating hypochlorite or hypobromite in aqueous media.

3. A composition in accordance with claim 1, wherein the aluminum content is supplied by strips of aluminum.

4. A composition in accordance with claim 1, wherein the metallic aluminum is in the form of a powder.

5. A composition in accordance with claim 2, which also includes about 0.5% to 5% by weight of a watersoluble low-foaming non-ionic organic detergent.

6. A method for treating glasses, dishes and glazed surfaces to remove foreign bodies from the surfaces thereof without modifying the substrata comprising treating said substrata with a dilute aqueous solution of the composition defined in claim 1.

7. A method of cleaning fine china and aluminum ware by washing with an aqueous solution of the composition defined by claim 4.

8. A method of safely cleaning fine china and aluminumware by washing with an aqueous solution of the composition defined in claim 3 in the presence of strips of aluminum.

9. A method in accordance with claim 6, which also includes a rinsing step.

References Cited UNITED STATES PATENTS 3,410,804 11/1968 Walsh 25299 MAYER WEINBLATT, Primary Examiner US. Cl. X.R. 25295, 

